package com.pbd.client.utils;




import java.util.ArrayList;
import java.util.List;

import com.google.gwt.core.client.JavaScriptObject;

/**
 * <p>
 * Implementation of the {@link java.util.regex.Pattern} class with a
 * wrapper aroung the Javascript <a href="http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Guide:Regular_Expressions">RegExp</a> object.
 * As most of the methods delegate to the JavaScript RegExp object, certain differences in the 
 * declaration and behaviour of regular expressions must be expected.
 * </p>
 * <p>
 * Please note that neither the {@link java.util.regex.Pattern#compile(String)} method nor
 * {@link Matcher} instances are supported. For the later, consider using {@link Pattern#match(String)}.
 * </p>
 * 
 * @author cogent
 *
 */
public class Pattern {

	/**
	 * Declares that regular expressions should be matched across line borders.
	 */
	public final static int MULTILINE = 1;

	/**
	 * Declares that characters are matched reglardless of case.
	 */
	public final static int CASE_INSENSITIVE = 2;

	private JavaScriptObject regExp;

	private static JavaScriptObject createExpression(String pattern, int flags) {
		String sFlags = "";
		if ((flags & MULTILINE) != 0)
			sFlags += "m";
		if ((flags & CASE_INSENSITIVE) != 0)
			sFlags += "i";
		return _createExpression(pattern, sFlags);
	}

	private static native JavaScriptObject _createExpression(String pattern,
			String flags)/*-{
	 return new RegExp(pattern, flags);
	 }-*/;

	private native void _match(String text, List matches)/*-{
	 var regExp = this.@com.pbd.client.utils.Pattern::regExp;
	 var result = text.match(regExp);
	 if (result == null) return;
	 for (var i=0;i<result.length;i++)
	 matches.@java.util.ArrayList::add(Ljava/lang/Object;)(result[i]);
	 }-*/;

	/**
	 * Determines wether the specified regular expression is validated by the 
	 * provided input.
	 * @param regex Regular expression
	 * @param input String to validate
	 * @return <code>true</code> if matched.
	 */
	public static boolean matches(String regex, String input) {
		return new Pattern(regex).matches(input);
	}

	/**
	 * Escape a provided string so that it will be interpreted as a literal
	 * in regular expressions.
	 * The current implementation does escape each character even if not neccessary,
	 * generating verbose literals.
	 * @param input
	 * @return
	 */
	public static String quote(String input) {
		String output = "";
		for (int i = 0; i < input.length(); i++) {
			output += "\\" + input.charAt(i);
		}
		return output;
	}

	/**
	 * Class constructor
	 * @param pattern Regular expression
	 */
	public Pattern(String pattern) {
		this(pattern, 0);
	}

	/**
	 * Class constructor
	 * @param pattern Regular expression
	 * @param flags 
	 */
	public Pattern(String pattern, int flags) {
		regExp = createExpression(pattern, flags);
	}

	/**
	 * This method is borrowed from the JavaScript RegExp object.
	 * It parses a string and returns as an array any assignments to parenthesis groups
	 * in the pattern's regular expression
	 * @param text
	 * @return Array of strings following java's Pattern convention for groups:
	 * Group 0 is the entire input string and the remaining groups are the matched parenthesis.
	 * In case nothing was matched an empty array is returned.
	 */
	public String[] match(String text) {
		List matches = new ArrayList();
		_match(text, matches);
		String arr[] = new String[matches.size()];
		for (int i = 0; i < matches.size(); i++)
			arr[i] = matches.get(i).toString();
		return arr;
	}

	/**
	 * Determines wether a provided text matches the regular expression
	 * @param text
	 * @return
	 */
	public native boolean matches(String text)/*-{
	 var regExp = this.@com.pbd.client.utils.Pattern::regExp;
	 return regExp.test(text);
	 }-*/;

	/**
	 * Returns the regular expression for this pattern
	 * @return
	 */
	public native String pattern()/*-{
	 var regExp = this.@com.pbd.client.utils.Pattern::regExp;
	 return regExp.source;
	 }-*/;

	private native void _split(String input, List results)/*-{
	 var regExp = this.@com.pbd.client.utils.Pattern::regExp;
	 var parts = input.split(regExp);
	 for (var i=0;i<parts.length;i++)
	 results.@java.util.ArrayList::add(Ljava/lang/Object;)(parts[i]	);
	 }-*/;
	
	/**
	 * Split an input string by the pattern's regular expression
	 * @param input
	 * @return Array of strings
	 */
	public String[] split(String input){
		List results = new ArrayList(); 
		_split(input, results);
		String[] parts = new String[results.size()];
		for (int i=0;i<results.size();i++)
			parts[i] = (String)results.get(i);
		return parts;
	}

	public String toString() {
		return regExp.toString();
	}
}

